Apparatus for dividing, compressing and transmitting video data

ABSTRACT

A first encoding section encodes an original picture S( 1 ) and outputs it to a communication line of a first channel. The encoded image data is decoded in a first decoding section. This decoded data C( 1 ) is input to a first compensation section. The first compensation section uses the original picture S( 1 ) and the decoded data C( 1 ) as the input, and performs calculation of the following expression (1) to thereby generate a first compensated original picture S( 2 ): 
               S   ⁡     (     i   +   1     )       =         (         S   ⁡     (   1   )       ×   i     -       ∑     k   =   1     i     ⁢     C   ⁡     (   k   )           )     /     (     N   -   i     )       +     S   ⁡     (   1   )                 (   1   )             
 
wherein i=2 to N, and N denotes the total number of channels in image encoding.
 
     The first compensated original picture S( 2 ) is encoded in a second encoding section and output from a communication line of a second channel. Thereafter, similar operation is performed for the total number of channels N. According to this invention, there can be provided an apparatus for dividing, compressing and transmitting video data that can sufficiently improve the encoding efficiency, without requiring preferential transmission of the basic data.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an apparatus for dividing, compressingand transmitting video data that improves encoding efficiency withoutrequiring preferential transmission of basic data.

2. Description of the Related Art

In an environment where the transmission quality largely varies(particularly, in an environment where the transmission speed varieslargely), a method for enabling reception of images having an imagequality corresponding to its quality has been heretofore studied, and asone method, application of scalability encoding has been tried.Conventional scalability encoding (hereinafter, referred to as “firstscalability encoding”) is divided largely into the followings:

1) time scalability capable of selecting the resolution in the directionof time stepwise;

2) space scalability for changing the space resolution;

3) data partitioning for dividing the frequency elements; and

4) SNR scalability for selecting encoding distortion stepwise.

However, these scalability encoding makes normal reception of the basicdata on a reception side a precondition. Therefore, on a transmissionside, it is necessary to transmit the basic data preferentially.

On the other hand, scalability encoding in which the above-describedbasic data is not necessarily transmitted preferentially (hereinafter,referred to as “second scalability encoding”) has been proposed. Thismethod is referred to as “flat multi-scalable encoding” and usestransmission using a redundant system. This method, however, transmitsdata encoded respectively independently, via a corresponding channel,respectively, and the reception side performs processing for averagingthese data. Therefore, there is a problem in that it is not sufficientin view of the encoding efficiency.

As described above, the first scalability encoding method has a problemin that the basic data must be transmitted preferentially, and thesecond scalability encoding method has a problem in that the encodingefficiency is not sufficient.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an apparatus fordividing, compressing and transmitting video data that can sufficientlyimprove the encoding efficiency, without requiring preferentialtransmission of the basic data.

In order to achieve the object, this invention is characterized in thatan apparatus for dividing, compressing and transmitting video data thatuses a plurality of channels for transmission, at least comprises: afirst encoding section for encoding an original picture and transmittingit with a first channel; a first compensation section for generating afirst compensated original picture obtained by adding and subtractingto/from said original picture a value obtained by dispersing an encodingerror occurred in said first encoding section to the remaining channels;and a second encoding section for encoding said first compensatedoriginal picture and transmitting it through a second channel.

According to the invention, an apparatus for dividing, compressing andtransmitting video data that can sufficiently improve the encodingefficiency without requiring preferential transmission of the basic datacan be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a construction of one embodiment ofthe present invention;

FIG. 2 is a diagram representing the operation on the transmission sidein FIG. 1;

FIG. 3 is a graph comparing the encoding efficiency by means of theconventional time scalability and the encoding efficiency obtained bythe present invention; and

FIG. 4 is a graph representing changes in the encoding efficiency ofpatterns 1, 2 and 3 obtained on the reception side.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention will now be described in detail, with reference tothe drawings. FIG. 1 is a block diagram showing a construction of oneembodiment of the present invention, and constructions on thetransmission side and on the reception side are shown. The presentinvention is characterized by the construction on the transmission side.

An encoding apparatus on the transmission side comprises: first, secondand third encoding sections 1, 2 and 3 in MPEG2 or the like; first,second and third decoding sections 4, 5 and 6 such as a local decoder inMPEG2 or a decoder for decoding a bit stream; and first, second andthird compensation sections 7, 8 and 9.

The first encoding section 1 encodes an original picture S(1) andoutputs it to a communication line 21 of a first channel. The encodedimage data is decoded in the first decoding section 4. This decoded dataC(1) is input to the first compensation section 7. To the firstcompensation section 7 are input the original picture S(1) and thedecoded data C(1). The first compensation section 7 performs calculationof an expression (1) described below to generate a first compensatedoriginal picture S(2). $\begin{matrix}{{S\left( {i + 1} \right)} = {{\left( {{{S(1)} \times i} - {\sum\limits_{k = 1}^{i}{C(k)}}} \right)/\left( {N - i} \right)} + {S(1)}}} & (1)\end{matrix}$where, i=2 to N, and N denotes the total number of channels in the imageencoding.

The first compensated original picture S(2) is encoded in the secondencoding section 2, and output from a communication line 22 of a secondchannel.

Then, the image data encoded in the second encoding section 2 is decodedin the second decoding section 5, and the decoded data C(2) is input tothe second compensation section 8. To the second compensation section 8are input the original picture S(1) and the decoded data C(1) and C(2).The second compensation section 8 performs calculation of the aboveexpression (1) to generate a second compensated original picture S(3).The second compensated original picture S(3) is encoded in the thirdencoding section 3, and output from a communication line 23 of a thirdchannel. The operation similar to that described above is performed foreach of the total number of channels N.

On the other hand, the reception side has decoding sections 51, 52, 53,. . . connected to each of the number of channels N, and to eachdecoding section 51, 52, 53, . . . are connected switches 54, 55, 56, .. . expressed simply. These switches 54, 55, 56, . . . represent thestate of the channel such as a mobile application, and if the channel isinterrupted due to some reason (for example, because it is in a shadowof a building), the switch is opened. The image data received by the Nchannel and decoded by the decoding section 51, 52, 53, . . . is addedby an adder 57 and averaged by an averaging section 58, and the imagedata is output as an output image signal R.

If the output image signal R is expressed by an expression, thefollowing expression (2) is obtained: $\begin{matrix}{R = {\sum\limits_{k = 1}^{N}{{C(k)} \times {{P(k)}/{\sum\limits_{k = 1}^{N}{P(k)}}}}}} & (2)\end{matrix}$where P(k) (k=1, . . . , N) is 0 (when data cannot be received) or 1(when data can be received).

FIG. 2 shows the operation on the transmission side in FIG. 1schematically. From this figure, it can be seen that the firstcompensated original picture S(2) becomes {(S(1)−C(1)}/(N−1)+S(1), andthe second compensated original picture S(3) becomes[{(S(1)−C(1)}+{(S(1)−C(2)}]/(N−2)+S(1). Looking at these first andsecond compensated original pictures S(2), S(3), it is seen that thefirst and second compensated original pictures S(2), S(3) are the onesobtained by adding to the original picture S(1) a value obtained bydispersing an encoding error occurred in the first and second encodingsections 1, 2 to the remaining channels.

Therefore, if the reception side decodes the encoded data of the Nchannel from the transmission side and adds these data for averaging,the encoding error occurred due to encoding on the reception side can becompensated as much as possible, and the encoding efficiency can besufficiently improved. Moreover, according to the present embodiment,each channel includes the original picture S(1), and it is obvious thatit is not required to transmit the basic data preferentially.

FIG. 3 shows the encoding efficiency of time scalability (channel 2) (adotted curve a), and time scalability (channel 3) (a dotted curve b),which is known to have excellent encoding efficiency, and the encodingefficiency of N=2 (curve c), N=3 (curve d), and N=4 (curve e) measuredin this embodiment. From this figure, it is seen that the encodingefficiency according to the present invention is not inferior to that ofthe time scalability. Moreover, it is seen that with an increase of N,SNR is improved.

FIG. 4 shows the encoding efficiency of each pattern, in the case whereQ (quantization step S size)=4, and N=5, and the reception side receiveswith pattern 1 of channel 1, channel 1+2, . . . , channel 1+2+3+4+5,pattern 2 of channel 1, channel 1+3, . . . , channel 1+3+5, and pattern3 of channel 5, channel 5+4, . . . , channel 5+4+3+2+1. Curves p, q andr in the figure show, respectively, encoding efficiency corresponding tothe pattern 1, 2 and 3. Moreover, for example, in the curve p, pointsp1, p2, p3, p4 and p5 show an SNR value at the time of receiving withch1, ch1+2, ch1+2+3, ch1+2+3+4 and ch1+2+3+4+5, respectively. Each pointon the other curves q and r is likewise.

As is obvious from the figure, since either of each curve p, q, r isupward slanting to the right, it is seen that as the number of channelsdecoded on the reception side increases, the encoding efficiency isimproved largely.

As is obvious from the above description, according to the presentinvention, an apparatus for dividing, compressing and transmitting videodata that can sufficiently improve the encoding efficiency withoutrequiring preferential transmission of the basic data can be provided.Moreover, there can be provided an image encoding and transmittingapparatus using multi-channels which give high synthetic image qualityon the reception side.

Moreover, according to the present invention, video data can be divided,encoded and transmitted, only by performing quite simple operation suchas arithmetic operation, other than normal encoding and decodingprocessing.

1. An apparatus for dividing, compressing and transmitting video datathat uses a plurality of channels for transmission, comprising: a firstencoding section for encoding an original picture and transmitting anencoded picture with a first channel; a first compensation section forgenerating a first compensated original picture obtained by adding tosaid original picture a value obtained by dispersing an encoding erroroccurred in said first encoding section to the remaining channels; and asecond encoding section for encoding said first compensated originalpicture and transmitting an encoded compensated picture through a secondchannel, wherein when said first compensated original picture isdesignated as S(2), said S(2) is expressed by the following expression(3);S(2)={(S(1)−C(1)}/(N−1)+S(1)  (3) wherein S(1) denotes an originalpicture, C(1) denotes decoded data, and N denotes the total number ofchannels.
 2. An apparatus for dividing, compressing and transmittingvideo data that uses a plurality of channels for transmission,comprising: a first encoding section for encoding an original pictureand transmitting an encoded picture with a first channel; a firstcompensation section for generating a first compensated original pictureobtained by adding to said original picture a value obtained bydispersing an encoding error occurred in said first encoding section tothe remaining channels; a second encoding section for encoding saidfirst compensated original picture and transmitting an encodedcompensated picture through a second channel, an i-th (i=2, 3, . . . ,N−1) compensation section for generating an i-th compensated originalpicture obtained by adding to said original picture a value obtained bydispersing an encoding error occurred in an i-th encoding section to theremaining channels; and an (i+1)-th encoding section for encoding saidi-th compensated original picture and transmitting an encoded i-thcompensated picture through an (i+1)-th channel, wherein when said i-thcompensated original picture is designated as S(i+1), said S(i+1) isexpressed by the following expression (4), $\begin{matrix}{{S\left( {i + 1} \right)} = \left\{ {{{S(1)} \times i} - {\sum\limits_{k = 1}^{i}{{C(k)}/\left( {N - i} \right)}} + {S(1)}} \right.} & 4\end{matrix}$ wherein S(1) denotes an original picture, C(k) denotesdecoded data, and N denotes the total number of channels.